1. Field of the Invention
The device of this invention resides in the area of sawdust-burning furnaces and more particularly relates to a furnace adapted to burn sawdust for the production of useful heat energy.
2. History of the Prior Art
At the present sawdust is a by-product of the lumber industry and is commonly found in quantity in the northern United States and Canada. Until recently sawdust has been treated as a waste product and a disposal problem. Efforts are now being made to utilize sawdust efficiently and one such use is as a fuel. Sawdust is similar to split wood as far as its ability to produce heat energy. When compared to other fuel sources, sawdust differs substancially in density as, for example, from wood and has the disadvantage of depositing heavy tar and creosote water mixtures when their condensation points are reached. A major advantage to the use of sawdust as a fuel source arises in the area of cost as sawdust is significantly less expensive than equivalent energy-producing amounts of wood or oil. It is therefore desirable that a furnace be developed that can efficiently utilize and burn sawdust in a manner that could be utilized in both industry and the home. Industrial users presently burn sawdust in the air by means of high pressure injection of the material into a furnace. Another means of burning sawdust has been by the use of conveyorized automatic feed of sawdust material to an area where it is surface burned in air. Small sawdust furnaces which are hopper-fed and surface burning have been utilized in homes. Double wall drum sawdust stoves have long been in use, mostly in other countries. These stoves use packed sawdust with a central hole for air circulation. These stoves burn well for a time, but due to the changing shape of the flue, they lose efficiency. See "Wood Waste As Fuel", leaflet No. 41, Revised June 1956, Forest Products Research Lab, Princes Risborough, Aylesbury, Bucks, England. Also see U.S.D.A. Forest Service Research Note Ne-208 on Double Drum Sawdust Stove by Jeffrey L. Wartluft. Also see Burmese Forester, 1946, page 14, "Wood Waste Utilization" by U. Win Maung. Also see Fulgora, Slow Combustion Stove, Great Britain, No. 595,869. Also see Sawdust Stove Photo Story, No. 30, Northeast Forest Experimentation Station, Upper Darby, PA. Also see U.S.D.A. Forest Service Memo of Mar. 6, 1980 on Chilean Sawdust Stoves. The usual problem, however, with surface, drum, or injection burning of sawdust as discussed above resides in the lack of uniformity of the sawdust particles, their varying moisture content, distillate deposits, and the presence of chips of wood mixed therein which cause significant problems with the uniformity and rate of burning and result in low burning efficiency.